Mobile Trojan mimics Android clean-up tool

Sneaky VXers spread infected version of security update

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Malware makers have released a Trojan version of an Android clean-up tool released by Google earlier this week.

Google pushed a security update (kill switch) that purged the DroidDream Trojan from infected handsets last weekend. DroidDream found its way onto the official Android marketplace, typically under the guise of mobile games, using an exploit to infect an estimated 50,000 handsets. The use of the exploit meant the attack was effective against Google Android smartphones, even if they weren't jailbroken.

In response, Google pulled the games from the marketplace. That stopped further infections from spreading but failed to help eradicate the infection from already compromised handsets, hence the decision to push an over-the-air update (theAndroid Market Security Tool).

But sneaky VXers have developed a backdoored version of this clean-up tool, dubbed Bgserv-A by security firms, and released through third-party Android marketplaces. Bgserv-A lifts the IMEI and the phone number from compromised handsets, uploading this information to a remote hacker-controlled server (much like the original Trojan). Analysis suggests that Bgserv-A is targeting users of Google's smartphone in China.

Infection is likely to lead to high data usage on infected devices, as well as posing a privacy risk. In-built functionality in the malware creates a means to send SMS messages from infected devices, under instructions from a command-and-control server.

A write-up of the malware can be found in blog posts by Symantec (here) and F-Secure (here). ®